Compositions incorporating dielectric additives for particle formation, and methods of particle formation using same

ABSTRACT

A method of forming particles that includes performing a strong force attenuation of a mixture to form pre-particles. The mixture including a base compound and a dielectric additive having an elevated dielectric constant dispersed therein. The pre-particles are then dielectrically spun in an electrostatic field to further attenuate the pre-particles and form the particles.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/966,895, filed Aug. 14, 2013 and entitled COMPOSITIONS INCORPORATINGDIELECTRIC ADDITIVES FOR PARTICLE FORMATION, AND METHODS OF PARTICLEFORMATION USING SAME, which claims the benefit of U.S. provisionalpatent application Ser. No. 61/682,894, filed Aug. 14, 2012 and entitledCOMPOSITIONS INCORPORATING DIELECTRIC ADDITIVES FOR PARTICLE FORMATION,AND METHODS OF PARTICLE FORMATION USING SAME, the entire contents allapplication which are hereby incorporated by reference herein for allpurposes.

FIELD

Embodiments herein relate generally to particle formation, and moreparticularly to compositions for particle formation that includedielectric additives, and methods of forming particles using suchcompositions.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments will now be described, by way of example only, withreference to the following figures, in which:

FIG. 1 is a schematic diagram illustrating a side view of an apparatusfor forming particles according to one embodiment;

FIG. 2 is a top view of a rotating disc of the apparatus of FIG. 1;

FIG. 3A is a graph of fiber distributions for pure polypropylene with noelectrostatic field applied during fiber formation;

FIG. 3B is a graph of fiber distributions for pure polypropylene with anelectrostatic field applied during fiber formation;

FIG. 4A is a graph of fiber distributions for a polymer compositionincluding polypropylene and a viscosity reducing additive with uppercowling air deactivated during fiber formation;

FIG. 4B is a graph of fiber distributions for the polymer compositionfrom FIG. 4A with upper cowling air active during fiber formation;

FIG. 5A is a graph of fiber distributions for a baseline polymercomposition including a dielectric additive and a dispersant without anelectrostatic field applied during fiber formation;

FIG. 5B is a graph of fiber distributions for the baseline polymercomposition from FIG. 5A with an electrostatic field applied duringfiber formation;

FIG. 5C is a graph of fiber distributions for a polymer compositionincluding a dispersant but no dielectric additive with an electrostaticfield applied during fiber formation;

FIG. 6A is a reproduction of FIG. 5B shown for comparative purposes;

FIG. 6B is a graph of fiber distributions for a polymer compositionincluding 2% ionic liquid;

FIG. 6C is a graph of fiber distributions for a polymer compositionincluding 5% ionic liquid;

FIG. 6D is a graph of fiber distributions for a polymer compositionincluding 10% ionic liquid;

FIG. 7A is a reproduction of FIG. 5B shown for comparative purposes;

FIG. 7B is a graph of fiber distributions for a polymer composition withionic liquid included within a polyglycerol-3 and sodium stearatedispersion;

FIG. 7C is a graph of fiber distributions for a polymer composition withionic liquid that is prepared according to a different mixing technique;

FIG. 8A is a reproduction of FIG. 5B shown for comparative purposes; and

FIG. 8B is a graph of fiber distributions for a polymer compositionincluding dielectric ceramic particles.

The embodiments shown in the figures are exemplary only, and should notbe construed as limiting the scope of the present disclosure or claims.

SUMMARY OF VARIOUS EMBODIMENTS

According to one embodiment, a method of forming particles, comprising:performing a strong force attenuation of a mixture to formpre-particles, the mixture including a base compound and a dielectricadditive having an elevated dielectric constant dispersed therein; thendielectrically spinning the pre-particles in an electrostatic field tofurther attenuate the pre-particles and form the particles. The strongforce attenuation may include mechanically attenuating the mixture. Insome embodiments, pre-particles may be micronic. In some embodiments,the particles are sub-micronic. In some embodiments, the base compoundis a polymer.

In some embodiments, the method further comprises melting the polymer toform a liquid polymer melt, then dielectrically spinning the liquidpolymer melt to form polymer particles.

In some embodiments, the mixture includes a dispersant selected toencourage the dielectric additive to disperse within the base compound.

In some embodiments, the pre-particles are formed using any suitablemelt blown technique.

In some embodiments, the pre-particles are formed using a rotating disc.

According to another aspect, acomposition for particle formation,comprising a base compound and a dielectric additive selected toencourage dielectrophoretic attenuation of the base compound duringdielectric spinning.

In some embodiments, the dielectric additive includes a mild dielectricadditive having a dielectric constant above 5. In some embodiments, thedielectric additive includes a moderate dielectric additive having adielectric constant above 10.

In some embodiments, the dielectric additive includes a strongdielectric additive having a dielectric constant above 100.

In some embodiments, the dielectric additive includes polyglycerol-3. Insome embodiments, the dielectric additive includes titanium dioxide(TiO₂). In some embodiments the dielectric additive includes bariumtitanate.

In some embodiments, the dielectric additive includes a ceramicdielectric. In some embodiments, the dielectric additive includeshigh-relative permittivity nanoparticles dispersed within the basecompound.

In some embodiments the composition further comprises a dispersantselected to aid in dispersing the dielectric additive within the basecompound. In some embodiments the dispersant includes sodium stearate.In some embodiments the dispersant includes sodium oleate.

In some embodiments the dispersant includes stearic acid. In someembodiments, the composition further comprises a viscosity-reductionadditive selected to reduce the viscosity of the base compound. Theviscosity-reduction additive may include Irgatec CR-76. Theviscosity-reduction additive may include peroxide.

In some embodiments the composition further comprises a conductivityadditive.

In some embodiments the composition further comprises an ionic liquid.In some embodiments the ionic liquid is mixed with the dielectricadditive.

In some embodiments a conductive additive is mixed with the dielectricadditive.

In some embodiments the composition is substantially solvent-free.

In some embodiments the composition comprises 85 to 99% by weight basecompound, and 0.5 to 20% by weight dielectric additive.

In some embodiments the composition comprises 0 to 5% by weightdispersant.

In some embodiments the composition comprises 0 to 10% by weightviscosity-reduction additive.

In some embodiments the base compound is a polymer.

In some embodiments the polymer is a thermoplastic polymer.

In some embodiments the base compound is selected from a groupconsisting of: polyethylene; polypropylene; polycaprolactone;co-polymers of polyethylene-acrylic acid; polyacrylonitrile; polyamides;polybutadiene; polycarbonate; polychloroprene;polychlorotrifluoroethylene; poly(ethylene terephthalate); polyisoprene;poly(methyl methacrylate); polyoxymethylene; poly(phenylene oxide);polystyrene; polysulfones; polytetrafluoroethylene; poly(vinyl acetate);poly(vinyl chloride); polyester; wax; polypyrrole; polyaniline;poly(vinylidene chloride); poly(vinylidene fluoride); co-polymers; andblends.

In some embodiments the base compound is selected from the groupconsisting of: liquid polymers; molten glasses; molten metals; moltensalts; minerals; ceramics; pure liquid substances; suspensions;emulsions; colloids; latex; solutions; and mixtures.

In some embodiments the dispersant is selected from the group consistingof sodium stearate and sodium oleate.

In some embodiments the dielectric additive is selected from the groupconsisting of: polyglycol; glycol; mannitol; ionic liquid;polycaprolactone; polyglycerol; glycerol; titanium dioxide; and bariumtitanate.

In some embodiments, the viscosity-reduction additive is selected fromthe group consisting of: Irgatec CR-76; peroxides; waxes; andlubricants.

According to another aspect, a method of forming particles, comprising:adding a dielectric additive to a base compound to form a mixture; anddielectrically spinning the mixture to form the particles.

In some embodiments the method further comprises mechanicallyattenuating the base compound before dielectrically spinning themixture. In some embodiments mechanically attenuating the base compoundforms particles larger than one micron, and the dielectric spinningforms particles smaller than one micron. In some embodiments themechanical attenuation forms particles less than 12 microns in diameter.In some embodiments the mechanical attenuation forms particles less than20 microns in diameter. In some embodiments the mechanical attenuationis performed using at least one rotating surface.

In some embodiments, the base compound is a polymer.

In some embodiments, the method further comprises melting the polymer toform a liquid polymer melt, then electrospinning the liquid polymer meltto form polymer particles.

In some embodiments the dielectric additives are added to the polymerbefore melting the polymer. In some embodiments the dielectric additivesare added to the polymer after melting.

In some embodiments the method further comprises adding a dispersantselected to encourage the dielectric additive to disperse within thebase compound.

In some embodiments the method further comprises mixing the dispersantand dielectric additive before the dielectric additive is combined withother ingredients.

In some embodiments the dispersant and dielectric additive are mixed,then combined with the base compound, and then mixed prior to meltingthe base compound.

In some embodiments the dispersant and dielectric additive are mixed,then combined with the base compound, and then mixed after melting thebase compound.

In some embodiments the method further comprises adding a viscosityreducing additive to base compound.

In some embodiments the particles include fibers.

In some embodiments the particles include droplets.

In some embodiments the base compound is selected from the groupconsisting of: liquid polymers; molten glasses; molten metals; moltensalts; minerals; ceramics; pure liquid substances; suspensions;emulsions; colloids; latex; solutions; and mixtures.

In some embodiments the method further comprises adding at least oneadditional compound. In some embodiments the at least one additionalcompound is selected from the group consisting of: carbon; activatedcarbon; super absorbent polymers; zeolites; bentonite; kaolin;diatomaceous earth chopped fibers; ion exchange resins; Teflon powder;adsorbents; absorbents; silicates; aluminas; minerals; ceramics; glass;and beads.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

As discussed in further detail below, various experiments were conductedby exposing different polymer compositions to an electrostatic field andobserving the resulting particle sizes.

In general, it was observed that using a dielectric additive can greatlydecrease the size of particles. More particularly, the effect of adielectric additive on particle size, particularly a non-conductivedielectric additive such as barium titanate, appears to be significant(especially as compared to a conductive additive), and suggests that atcertain particle sizes dielectrophoretic forces become dominant.

In some cases, very small particles may be formed in a two-part processin which a liquid mixture (which includes dielectric additives) is firstmechanically attenuated to form pre-particles, particularly micronicpre-particles. These pre-particles are then subjected to anelectrostatic field (e.g., dielectrically spun) to form smallerparticles, particularly sub-micronic particles.

In general, the term “particles” as generally used herein includesfibers (e.g., filaments, ligaments, etc.), droplets, and other similarshapes made from any suitable liquid (e.g., polymer melts, etc.) andwhich may solidify, evaporate, and/or remain in liquid form.

“Electrospinning” conventionally refers to the production of particles(e.g., fibers or droplets) that are “spun” as fibers or “sprayed” asdroplets by applying high electrostatic fields to one or more fluidspraying or spinning tips (e.g., emitters or spinnerets). The sprayeddroplets or spun fibers are typically collected on a target substrate orcollector plate positioned away from the emitters, in some cases by adistance of a few millimeters, a few centimeters or more.

A high voltage supply provides an electrostatic potential difference(and hence the electrostatic field) between the emitter (usually at highvoltage, either positive or negative) and the target substrate (usuallygrounded). In some embodiments, the spinning emitter can be groundedwhile a high voltage is applied to the substrate.

It is often desirable to produce particles of very small sizes,particularly particles having a diameter less than 1 micrometer (i.e.,sub-micron particles).

Theoretically this should be possible with various known electrospinningprocesses based on laboratory results. However, in practice scaling upbeyond the laboratory or prototype level of an electrospinning processthat employs conventional, relatively conductive fluid compositions hasproven to be problematic, particularly when trying to produce very smallparticles in large quantities.

One approach to small particle production is to dissolve a targetparticle material (e.g., a polymer) in a solvent. The solvent and targetmaterial are then subjected to an electrospinning process to formparticles, after which the solvent will separate or evaporate from theparticles to reduce the overall particle size.

However, this process can involve the use of fairly toxic solvents, andprocessing these solvents can be problematic, especially when generatingsignificant quantities of particles. There are especially concerns aboutthe dangers of ignition or combustion at elevated solventconcentrations.

Moreover, significant energy is expended to electrospin a material (thesolvent) that is wasted using this technique, and the fiber productionrates are normally quite small. In particular, the solvent normallycontributes the bulk of the material (e.g., 80-85 wt %) while thepolymer is normally between about 15-20 wt %. Thus, a large portion ofthe material composition in solvent electrospinning is simply wasted.

Conventionally, another approach to the production of very small fibersis achieved using conductivity-driven fiber attenuation of polymermelts, commonly referred to as melt electrospinning. However thisapproach typically requires that the polymer melt have a high electricalconductivity, which is hard to achieve as polymers tend to be insulativein nature.

One approach to increasing the electrical conductivity of a polymer meltis to add conductive additives to increase its electrical conductivity.For example, as discussed in PCT application no. PCT/CZ2011/000070 toPlistil et al., 1-25% by weight of a conductive agent can be added to apolymer melt.

However, these conductive additives can cause further problems. Forexample, conductive additives tend not to be thermally stable, and canbreak down at the elevated temperatures within a polymer melt, degradingfiber production. Furthermore, conductive additives can be veryexpensive, in some cases approaching eighty dollars per pound or more,and some may be highly toxic.

Finally, to achieve desired electrospinning performance, conductiveadditives may need to be included in very high concentrations. However,this can have a negative impact on the mechanical properties of theresulting particles, which is undesirable.

Accordingly, at least some of the teachings herein have been directed tothe production of very small particles, particularly sub-micron fibers,without needing solvents or conductive additives.

Turning to FIGS. 1 and 2, illustrated therein is a schematicrepresentation of an apparatus 10 for forming particles according to oneembodiment.

The apparatus 10 generally includes at least one rotating surface, whichin this embodiment is a rotating disc 12 with an upper surface 14. Theapparatus 10 also includes a feed chamber or dispenser 16. As shown, thedispenser 16 is generally at or near the center of the disc 12 (e.g. atthe axis of rotation A of the disc 12) and serves as a source for theliquid polymer used to feed the apparatus 10.

In particular, a liquid polymer (indicated generally as M) may bedeposited from the dispenser 16 onto the surface 14 of disc 12 generallyat the axis of rotation A. The deposited polymer M will then flowoutwardly across the disc surface 14, generally as a thin film, due tothe centrifugal forces generated by rotation of the disc 12.

For select operating conditions (e.g., rotational speeds, polymer feedrates, etc.), upon reaching the edge 18, the liquid polymer M willseparate from the surface 14 of the disc 12 to form particles (indicatedgenerally as P). In various embodiments, these particles P may includefibers (e.g. filaments, ligaments, fibrils, etc.), droplets, orparticles of various other shapes and sizes.

An electrostatic field is then applied to further attenuate theseparticles P. For example, an electrostatic field may be generatedbetween the disc 12 and a collector plate 20 positioned below the disc12. Due to the electrostatic field, and when the liquid polymer M has asuitable composition, the particles P ejected from the disc 12 willattenuate within the electrostatic field so as to further reduce insize. For example, particles P may be ejected from the disc 12 with asize greater than one micron in diameter (e.g., greater than one micronbut generally less than fifty microns), and then be further attenuatedby the electrostatic field to have a diameter of less than one micron.

The particles P will normally be drawn down by the electrostatic fieldand deposit on a top surface of the collector plate 20, in some casesforming a particle mat T on the collector plate 20.

In some embodiments, an estimate of the electrostatic field strength forthe apparatus 10 may be indirectly determined by a voltage-distancequotient, shown here as the disc-to-collector distance DCD between thecollector plate 20 and the disc 12.

Generally, the particle mat T may be considered as having an innerregion IR, an outer region OR, and a middle region MR. In some cases,the properties of the particles P deposited in each region will vary.For example, smaller particles may be slowed more quickly by the airsurrounding the disc 12 and tend to collect in the inner region IR,while larger particles may have more inertia and travel further from thedisc 12, tending to settle in the outer region OR (although in manycases the distribution of particle sizes can be highly variable acrossthe regions of the mat T).

In some embodiments, hot or warm air may be introduced through one ormore cowlings 22, 24 surrounding at least a portion of the disc 12 andthe dispenser 16. For example, as shown hot air is ejectedradially-outwardly from an upper cowling 22 above the surface 14 of thedisc 12 and from a lower cowling 24 below the disc 12. This air can helppromote attenuation of the particles P due to the momentum from thevelocities Uo₁ and Uo₂ of the upper and lower air.

The hot air helps heat the disc 12 and dispenser 16 to maintain thepolymer M in a liquid state, and more particularly at a temperature andviscosity that encourages the formation of small and stable particles Pthat separate from the edge 18 of the disc 12.

The hot air can also heat the ambient air surrounding the disc 12. Thisheating can encourage the molten particles P that have separated fromthe disc 12 to further attenuate within the electrostatic field beforesolidifying and depositing on the collector plate 20.

Experiments

General Comments

A series of experiments were conducted making use of several differentcompositions of liquid polymers for particle production, particularlyfiber production. These experiments were performed using an apparatusgenerally similar to the apparatus 10 of FIG. 1 in varying operatingconditions as detailed below.

A relative assessment of the liquid polymer compositions was thenperformed by subsequently comparing observed results (e.g., aggregatemean fiber diameter estimates obtained from fiber samples for eachrespective polymer composition and fiber distributions).

In some cases, a particular polymer composition may be considered to berelatively more effective at attenuating fibers if the resultingaggregate mean fiber diameter, fiber distribution and/or standarddeviation is generally smaller than that obtained from another polymercomposition.

In some experiments discussed below, the hot air provided by the uppercowling was deactivated just prior to initiating particle formation.This was done to decrease the radial momentum exerted on the moltenparticles separating from the edge of the disc without significantlychanging the polymer viscosity or ambient air temperature.

For the experiments discussed below, the disc-to-collector distance DCDwas approximately 7.8 cm, while the disc was a 6″ disc held at aconstant speed of 2000 rpm. It should be noted that unless otherwiseindicated, all experiments involved an active electrostatic field usingthe apparatus in a “cold-head” configuration, wherein high-voltage wasapplied to the collector plate 20 (+36 kV), while the dispenser 16 androtating disc 12 were grounded. In particular, a positive voltage wasapplied to the collector plate 20, thus generating a negativeelectrostatic field with field lines directed from the collector plate20 to the disc 12.

In some embodiments other electrostatic field configurations could beused (e.g. a “hot-head” configuration, wherein high-voltage is appliedto the dispenser 16 and rotating disc 12, while the collector plate 20is grounded). Moreover, the polarity of the applied voltage could bepositive or negative in various different embodiments.

It has been observed that the field direction and polarity can have amarginal effect on the particle size. More particularly, it has beenobserved that a “hot-head” configuration may provide smaller particlesin some operating conditions, particularly when a negative electrostaticfield is generated, although this can be more challenging configurationto implement.

A fiber production rate may be characterized by measuring the mass ofparticles deposited on the collector plate within a particular period oftime (e.g., within 1 minute). Since most experiments presented here wereperformed in the presence of an electrostatic field, the majority of thefibers produced were deposited on the collector plate with a marginalamount of stray fibers. Thus, for most embodiments, the “fiberproduction rate” can also be characterized as a “polymer depositionrate”, or simply the “flow rate”, since the mass of polymer wasgenerally conserved.

On the other hand, for cases without an applied electrostatic field,many of the fibers were not deposited on the collector plate, but wereinstead deposited on other surfaces of the apparatus (e.g., a cover orlid of the apparatus). In such cases, the fiber production rate ordeposition flow rate may be taken by collecting the fibers deposited onthe various surfaces of the apparatus.

In general, it has been determined that statistically-steady averagefiber diameter estimates can be obtained with reasonable certainty for asample population of at least 100 fiber diameters (with a measurementuncertainty of approximately ±100 nm). For these experiments, anaggregate fiber diameter distribution and average were obtained bycombining the fiber diameter distributions from the inner region IR,middle region MR and outer region OR. Sampling locations were selectedsuch that the average was based on a sample population of at least 300diameter measurements. The observed aggregate fiber distributions arereproduced in FIGS. 3 to 8 as discussed in greater detail below.

For greater certainty, Table 1 below lists various chemicals asdiscussed herein along with some associated properties. It should benoted that the functional properties of relative permittivity andconductivity are shown at room temperature and not in the presence of anelectrostatic field. These relative permittivity and conductivity valuesare used as estimates since the experiments were conducted for a rangeof temperatures and voltage magnitudes within which these parametervalues are unknown and may have varied.

It should also be noted that for the components sodium stearate andphosphonium-based ionic liquid, relative permittivity and conductivityparameters could not be determined. However the relative permittivity ofstearic acid, which is chemically similar to sodium stearate, isbelieved to be approximately 2.7 as was used as prediction. Similarly,the relative permittivity of a phosphonium-based salt is approximately10-15, while the conductivity of nitrogen-based imidazolium is 400μS/cm; these properties were used as predictors for the ionic liquid.

TABLE 1 Chemical Ingredients Dielectric Constant/ CAS RelativeConductivity Acronym Chemical Identity number Permittivity [μS/cm] PPpolypropylene homopolymer 9003-07-0 2.3-2.7 3.38 × 10⁻⁶ (MetoceneMF650Y) IRGTC hydroxylamine derivative trade secret — — (Irgatec CR-76)PG-3 polyglycerol-3 25618-55-7  30 — SS sodium stearate 822-16-2 2.7 —(stearic acid) IL trihexyl(tetradecyl)phosphonium bis 465527-58-6 10-15400 2,4,4-(trimethylpentyl)phosphinate (phosphonium (imidazolium (ionicliquid) salt) ionic liquid) BaTiO₃ barium titanate 12047-27-7 1750 —

Experiment 1: Pure Polypropylene

In a first experiment, fiber was collected in two tests 1 a and 1 busing an apparatus similar to the apparatus 10 described above. The basecompound was 100% polypropylene (pure polypropylene), mixed at highshear at 265 degrees Celsius for 1 minute. Other parameters for thesetests are listed below in Table 2: Polypropylene mixtures:

TABLE 2 Polypropylene mixtures Fiber Diameter Flow Standard Test MixtureRate Voltage Uo₁/Uo₂ Average Deviation ID Composition [g/min] [kV] [m/s][nm] [nm] 1a 100% PP 1.6 0 4.0/4.3 5538 3941 1b 100% PP 1.8 +36 4.0/4.310742 7818

The resulting fiber diameter distributions are shown in FIG. 3A for thefirst test 1 a without an electrostatic field and FIG. 3B for the secondtest 1 b with an electrostatic field.

In both cases, the bulk of the fibers were micronic fibers, with fiberdiameters greater than 1000 nanometers. In fact, the vast majority offibers were larger than 4000 nanometers in diameter, while the averagefiber diameters were over 5500 nanometers and 10700 nanometers.

In the first test 1 a, without the electrostatic field, the fibers wereejected radially outwardly from the disc and followed an upwardtrajectory due to buoyant plumes and vortices of air, eventuallycollecting on a lid of the apparatus.

However, in the second test 1 b, the fibers deposited on the collectorplate due to the presence of the electrostatic field. These observationssuggest that some surface charge exists on the pure polypropylenefibers, resulting in some fiber trajectory control when thepolypropylene is exposed to the electrostatic field.

However, the surface charge appears fairly weak and is likelyinsufficient to attenuate pure polypropylene fibers to the desired smallfiber sizes.

Experiment 2: Polypropylene with Viscosity Reduction Additive

The first experiment showed that micronic fibers were produced using apure polypropylene melt, regardless of the presence of an electrostaticfield. This suggests that the fibrils and other particles ejected fromthe rotating disc are initially fairly large, thus compromising thelikelihood of attenuating ejected pure polypropylene particles andfibers to a sub-micronic size.

The second experiment investigated whether fiber diameter reductioncould be promoted by decreasing the viscosity of the polymer melt usinga viscosity-reduction additive. For this experiment, 5 wt % IrgatecCR-76 (5% by weight), produced by BASF, was selected as theviscosity-reduction additive and was added to the base compound (95 wt %PP). The polypropylene and Irgatec CR-76 were high-shear mixed togetherfor 3 min at 265 degrees Celsius prior to being fed through thedispenser.

Additional parameters for the two tests with Irgatec CR-76 are shown in*upper cowling air (Uo1) turned off during particle formation

Table 3: Polypropylene and 5% Irgatec CR-76 mixture. Both tests includedthe presence of an electrostatic-field, however in the first test (test2 a) the upper-cowling air (Uo₁) was deactivated during particleformation.

TABLE 3 Polypropylene and 5% Irgatec CR-76 mixture Fiber Diameter FlowStandard Test Mixture Rate Voltage Uo₁/Uo₂ Average Deviation IDComposition [g/min] [kV] [m/s] [nm] [nm] 2a 95% PP 0.7 +36   */4.3 23841808 5% IRGTC 2b 95% PP 3.7 +36 4.0/4.3 7324 5439 5% IRGTC *uppercowling air (Uo₁) turned off during particle formation

The resulting fiber diameter distributions are shown in FIGS. 4A and 4Bfor the first test 2 a and second test 2 b, respectively.

In the first test, it is worth noting that with the upper cowling airdeactivated, the polymer melt barely emerged from the dispenser, havinga flow rate of only approximately 0.7 g/min.

On the other hand, when the upper cowling air was active during thesecond test, the flow rate increased to 3.7 g/min, more than double theflow rate of pure polypropylene at comparable operating conditions (seetest 1 b results). This suggests that 5 wt Irgatec CR-76 reduces theviscosity of the polypropylene polymer melt.

However, it was also observed that the average fiber size increased fromaround 2300 nm to 7300 nm between the two tests. This is likely due tothe low flow rate in the first test, since at a flow rate of only 0.7g/min, the rotating disc was effectively “starved” of polymer, resultingin smaller fibers.

Further comparisons of tests 2 b and 1 b suggest that theviscosity-reduction additive reduces the average fiber size. However,the reduction is somewhat marginal, as with the Irgatec CR-76 the fiberswere only about 3000 nm smaller than the pure polypropylene fibers. Thismarginal reduction suggests that while Irgatec CR-76 reduces polymerviscosity, this is insufficient to promote the desired fiber attenuationto sub-micronic particles.

Supplemental experiments (not detailed here) have confirmed thatincreasing the concentration of Irgatec CR-76 above 5 wt % could producefibers with diameters in the range of 1000 nm to 3000 nm. However, nosub-micron fibers were obtained simply by increasing the Irgatec CR-76concentration. Furthermore, at elevated Irgatec CR-76 concentrations,the resulting fiber strength seemed to decrease significantly. Thus,simply reducing the viscosity of a polymer melt may be insufficient toachieve the desired sub-micronic fibers.

Experiment 3-Dielectrophoretic-driven Fiber Attenuation

The results of the second experiment suggested that in order to obtainsub-micronic particles or fibers, additional force mechanisms beyondcentrifugal and aerodynamic forces may be necessary.

In the third experiment, tests were conducted using a polymercomposition that added two additional components, a dielectric additiveand a dispersant. In particular, the resulting composition included thebase compound (e.g., polypropylene), a viscosity reduction additive(e.g., Irgatec CR-76), a dielectric additive (e.g., polyglycerol-3), anda dispersant (e.g., sodium stearate) selected to aid in dispersing thedielectric additive within the polymer melt.

For convenience, the combination of these four compounds in a polymermelt composition will be referred to as a “baseline” mixture, withvarious different concentrations of the compounds possible.

Additional parameters for these tests are listed in Table 4: DielectricDriven Mixture (Baseline Mixture) below:

TABLE 4 Dielectric Driven Mixture (Baseline Mixture) Fiber Diameter FlowStandard Test Mixture Rate Voltage Uo₁/Uo₂ Average Deviation IDComposition [g/min] [kV] [m/s] [nm] [nm] 3a 90% PP 4.2 0 4.0*/4.3 127372105 5% IRGTC 4% PG-3 1% SS 3b 90.5% PP 4.2 +36 4.0*/4.3 620 908 4% PG-35% IRGTC 0.5% SS 3c 94.5% PP 1.4 +36 4.0*/4.3 7984 4244 5% IRGTC 0.5% SS*upper cowling air (Uo₁) turned off during particle formation

In the presence of an electrostatic field, it was suspected that thebaseline mixture should respond to dielectrophoretic forces in additionto the centrifugal and aerodynamic forces.

Experiments with baseline formulations were conducted in tests 3 a and 3b without and with an electrostatic field, respectively. The resultingfiber distributions are shown in FIGS. 5A and 5B respectively.

Similar to the experiments performed with pure molten polypropylene, inthe first test 3 a (without an electrostatic field) the resulting fiberswere generally micronic, with an average fiber diameter in excess of12,000 nanometers.

However, the results were very different when the electrostatic fieldwas applied. In particular, as evident by inspection of FIG. 5B, theelectrostatic field resulted in a significant drop in the average fiberdistribution for the baseline mixture in the second test 3 b, and mostobserved fibers were less than 650 nm in diameter, with a substantialconcentration below 250 nanometers.

Moreover, the average fiber diameter dropped from over 12,000 nm toaround 620 nm, a reduction of about 95%.

These findings suggest that strong fiber attenuation has occurred due tothe specific polymer composition. Based on an inspection of thefunctional properties of the ingredients for the baseline mixture(listed in Table 1 above), it appears that the dielectrophoretic forceassociated with the moderate dielectric additive material(polyglycerol-3) may be responsible for driving sub-micronic fiberattenuation.

To confirm this hypothesis, a further test 3 c was performed incomparable operating conditions as in test 3 b using a generally similarpolymer composition but without the dielectric additive (i.e., nopolyglycerol-3 was added to the composition).

FIG. 5C shows the resulting fiber diameter distribution for test 3c. Asshown, the fibers were much larger, with most fibers having a diameterof over 4000 nanometers and with an average diameter of nearly 8000nanometers.

This further suggests that it was the dielectric additive (e.g., thepolyglycerol-3) that was largely responsible for the sub-micronic fiberattenuation, particularly due to the associated dielectrophoreticforces.

Additional tests were conducted (not detailed here) with a baselineformulation at 7 wt % polyglycerol-3 for a range of voltage magnitudes,without reviewing fiber distributions. Generally, as the voltageincreased from +20 kV to +40 kV, the flow rate also increased (from 4.7g/min to 7.2 g/min). This increase in flow rate suggests that increasingthe electrostatic-field strength increases the dielectrophoretic forcesin the material and the tendency to pull molten particles towards thecollector plate.

Experiment 4—Ionic Liquid Mixtures for Conductivity Attenuation

Conventionally, sub-micron fiber production using polymer melts has beenattempted using conductivity-driven fiber attenuation, commonly referredto as melt electrospinning. However, it has been challenging to makesuch processes work in a real-world setting, especially since it isdifficult to make conductive polymer melts.

To explore conductivity-driven fiber attenuation, and in particular tocompare that approach to the polymer composition in experiment 3, testswith phosphonium-based ionic liquid concentrations of 2%, 5%, and 10 wt% were performed (as presented in Table 5 below). For comparativepurposes, the results of test 3 b with a baseline composition aredisplayed in the same table.

TABLE 5 Ionic Liquid Mixtures Fiber Diameter Flow Standard Test MixtureRate Uo₁/Uo₂ Average Deviation ID Composition [g/min] [m/s] [nm] [nm] 3b90.5% PP 4.2 4.0*/4.3 620 908 4% PG-3 5% IRGTC 0.5% SS 4a 93% PP 2.74.0*/4.3 1934 1687 5% IRGTC 2% IL 4b 90% PP 4.6 4.0*/4.3 5076 3966 5%IRGTC 5% IL 4c 85% PP 4.2 4.0*/4.3 2674 1777 5% IRGTC 10% IL *uppercowling air (Uo₁) turned off during particle formation

Fiber distributions for the baseline test and for tests 4 a, 4 b, and 4c are shown in FIGS. 6A to 6D, respectively.

These results indicate that the inclusion of a conductive additive suchas an ionic liquid does indeed have an effect on fiber attenuation,since there is a measureable fiber diameter reduction relative to purepolypropylene. However, comparing these results with the baselineformulation from test 3 b suggests that the conductive additives (andthe associated Coulomb force) have a much weaker effect on fiberattenuation relative to dielectrophoretic-forces provided by thedielectric additives.

In particular, it is notable that even at ionic liquid concentrationsapproaching 10 wt %, the average fiber size was over 2600 nanometers,and most fibers were micronic.

Experiment 5—Baseline Mixture Combined with Ionic Liquid

Experiments 3 and 4 indicated that fiber attenuation can be driven byboth dielectrophoretic and Coulomb force mechanisms. Experiment 5 aimedto determine if the Coulomb forces (due to the conductive additives)could be coupled with dielectrophoretic forces with additive effect todrive fiber attenuation into a deeper sub-micron regime.

TABLE 6 Baseline Mixture with Ionic Liquid Fiber Diameter Flow StandardTest Mixture Rate Uo₁/Uo₂ Average Deviation ID Composition [g/min] [m/s][nm] [nm] 3b 90.5% PP 4.2 4.0*/4.3 620 908 4% PG-3 5% IRGTC 0.5% SS 5a88.5% PP 4.6 4.0*/4.3 609 1265 4% PG-3 5% IRGTC 0.5% SS 2% IL 5b 88.5%PP 3.1 4.0*/4.3 724 961 4% PG-3 5% IRGTC 0.5% SS 2% IL

Two experiments were conducted with ionic liquid and polyglycerol-3 withthe same compositions but different formulation preparation procedures.Specifically, for the first formulation in test 5 a, ionic liquid wasadded to polyglycerol-3 and sodium stearate before combining withpolypropylene and Irgatec CR-76 pellets and stirring these ingredients.

For the next test 5b, the ionic liquid was not mixed with polyglycerol-3and sodium stearate, but instead was added to the Irgatec CR-76 andpolypropylene pellets separately, followed by stirring of thesecollective ingredients.

The corresponding fiber diameter distributions are shown in FIGS. 7B and7C. The results of the first test 5a indicate that there is a marginaldifference in the fiber size obtained when the ionic liquid is mixedwith the dielectric additive and the dispersant. However, when the ionicliquid was added separately the result was actually an increase in fibersize.

These findings suggest that the addition of an ionic liquid results in arelatively weak force mechanism that does not significantly drive fiberattenuation any deeper. In fact, the attenuation due todielectrophoretic forces appears to remain dominant.

Experiment 6—Baseline Mixtures with Ceramic Dielectric Additive

Experiments 4 and 5 suggested that conductivity-driven attenuation(e.g., due to conductive additives) is relatively weak in comparison todielectrophoretic-driven attenuation (e.g., due to dielectricadditives).

To investigate this further, a high relative permittivity (dielectricconstant) ceramic particle (50 nm barium titanate, BaTiO₃) was added tothe baseline mixture to further drive attenuation by attempting toenhance dielectrophoretic forces.

Barium titanate has very high relative permittivity (dielectricconstant) of approximately 1750, and is not considered to be anespecially good conductor. In particular, when barium titanate isdispersed at concentrations of less than 1 wt % in molten polymer, thisceramic powder makes no contribution to the bulk conductivity of thepolymer.

TABLE 7 Baseline Mixture with Ceramic Dielectric Fiber Diameter FlowStandard Test Mixture Rate Uo₁/Uo₂ Average Deviation ID Composition[g/min] [m/s] [nm] [nm] 3b 90.5% PP 4.2 4.0*/4.3 620 908 4% PG-3 5%IRGTC 0.5% SS 6a 90% PP 3.3 4.0*/4.3 431 641 4% PG-3 5% IRGTC 0.5% SS0.5% BaTiO₃ (50 nm) *upper cowling air (Uo₁) turned off during particleformation

The results for this experiment are shown in Table 7 for the baselinemixture alone and with added barium titanate (BaTiO₃). Fiberdistributions are shown in FIGS. 8A and 8B.

For comparable operating conditions, adding barium titanate yielded ameasurable reduction in the average fiber diameter from 620 nm to 431nm. Inspection of the fiber diameter distribution in detail suggeststhat the reduction in fiber diameter is largely due to the furtherattenuation of larger micronic fibers to smaller sub-micronic fibers, asevidenced by the decrease in the micronic fiber population in FIG. 8B.

In addition, the population of fibers centered around 150 nm increasedby approximately 10%, which suggests that the barium titanate doescontribute to relatively deep sub-micronic fiber attenuation.

However, sub-micronic fiber formation below approximately 150 nm was notobserved. This suggests that a lower attenuation-limit may have beenreached for this particular polymer composition.

There are several theories that may explain this. First, since theviscosity of a polymer melt increases rapidly as the particles separatefrom the disc and quickly transition from a hot region (on the disc) toa colder region (in ambient air), there may be insufficient time for theparticles to fully attenuate in the presence of BaTiO₃.

Furthermore, the BaTiO₃ particles used in this experiment are ratherlarge (approximately 50 nm in diameter), which may have impeded thereduction of fiber sizes due to poor barium titanate dispersion withinthe polymer melt.

It may also be more difficult to generate a motive dielectrophoreticforce in a large barium titanate particle to stimulate sufficientmomentum to overcome viscous forces in polymer melt. However, if asmaller diameter high-relative permittivity nanoparticles can beadequately dispersed within a polymer melt, it may be possible to driveparticle sizes even smaller than is presently observed

Summary of Experimental Results and Discussion

The results for the six experiments and the observed attenuationmechanisms are summarized in Table 8 below.

In general, various degrees of attenuation of polymer particles may beachieved via centrifugal, aerodynamic, Coulombic and dielectrophoreticmechanisms. However, as discussed above, particularly with reference toexperiments 3 to 6, dielectrophoretic attenuation (through the additionof dielectric additives) appears to be particularly suitable forgenerating sub-micronic particles and fibers.

TABLE 8 Summary of Experimental Test Cases Test Case DescriptionAttenuation Mechanisms Experiment 1 PP centrifugal aerodynamicExperiment 2 PP + viscosity reduction centrifugal additive aerodynamicExperiment 3 PP + viscosity reduction centrifugal additive + dielectricaerodynamic additives dielectrophoretic Experiment 4 PP + viscosityreduction centrifugal additive + conductive aerodynamic additivesCoulomb Experiment 5 PP + viscosity reduction centrifugal additive +dielectric & aerodynamic conductive additives dielectrophoretic CoulombExperiment 6 PP + viscosity reduction centrifugal additive + multipledielectric aerodynamic ingredients (with strong dielectrophoreticdielectic contrast)

Therefore, it would appear that various compositions that includedielectric additives may provide for good production of small particles,particularly sub-micronic particles.

In some embodiments, a suitable composition for particle formation cangenerally be described as including a base compound (e.g., a polymer oranother suitable target material for the particles) and at least onedielectric additive.

The dielectric additive should be selected to encouragedielectrophoretic attenuation during spinning of the base compoundwithin an electrostatic field (e.g., dielectric spinning) when the basecompound is in a liquid form (e.g., a polymer melt). In particular, thedielectric additive should have a dielectric constant that is higherthan the dielectric constant of the base compound, particularly for theoperating parameters of the spinning apparatus (e.g., elevatedtemperatures, etc.).

In general, the process of spinning in an electrostatic field in thepresence of a dielectric additive can be referred to as “dielectricspinning”.

In general, the dielectrophoretic mechanism in dielectric spinning isnot enhanced by using an electrically conductive base compound. In fact,dielectric spinning may be positively enhanced when the conductivity ofthe mixture is very low, and in particular generally much lower than theconductivity of liquids normally used in conventional electrospinningtechniques.

In fact, there may be no particular advantage to using a base compoundor mixture with an elevated electrical conductivity, as dielectricspinning may in fact favor fluids with low electrical conductivity.

In different embodiments, the dielectric additive could have differentproperties. For example, the dielectric could be a mild dielectric(e.g., defined as having a dielectric constant above 5), a moderatedielectric (e.g., defined as having a dielectric constant above 10), ora strong dielectric (e.g., defined as having a dielectric constant above100). In some cases, the dielectric additive may have a dielectricconstant above 1000 or more.

In some embodiments, possible dielectric materials for use in dielectricspinning could include one or more of the materials listed below inTable 9.

TABLE 9 Alternative Dielectric Additive Materials Relative permittivity/Conductivity dielectric constant Material [μS/cm] (approx.) ionic liquid400 10-15  Polycaprolactone Polyglycerol 30 glycerol 40 titanium dioxide(TiO₂) 4000 86-173

In some compositions, a dispersant (e.g., sodium stearate, sodiumoleate) may be added to aid in dispersing the dielectric additive withinthe base compound. In particular, it may be beneficial for thedielectric additive to be homogenously dispersed within the basecompound, and the dispersant may encourage such dispersion.

In some compositions, other compounds (e.g., viscosity reducingadditives, conductive additives, etc.) can be added to the composition,for example as generally described above. For a polymer, some viscosityreducing additives could include Irgatec CR-76, peroxides, or generallyanything that decreases the molecular weight of the polymer chains in apolymer melt, or lubricants.

In general, such compositions can be electrically attenuated without theneed for solvent, and thus are generally “solvent-free”. In general,“solvent-free” generally means that the composition does not include asignificant amount of solvent.

More particularly, as compared with other known techniques, indielectric spinning the compounds in the polymer composition are trulyblended, and there is little or no “ejection” or “evaporation” of any ofthe components after the particles have been formed. The finishedparticles and fibers will thus include both the base compound, thedielectric additive, and any dispersants or other compounds generallyadded to the composition before dielectric spinning.

In some embodiments, a generally insignificant or trace amount ofsolvent may still be present in a composition considered “solvent-free”.For example, a composition may contain less than 0.5 wt % solvent orless than 0.1 wt % solvent.

In various embodiments, suitable compounds can contain differentconcentrations of the various components. For example, in one embodimenta suitable compound may include 85 to 99% by weight base compound (e.g.,polypropylene or another polymer), and 0.5 to 20% by weight dielectricadditive (e.g., triglycerol, glycerol). The composition might alsoinclude 0 to 5 % by weight dispersant, and 0 to 10 % by weightviscosity-reduction additive.

In some embodiments, the base compound includes a polymer, particularlya thermoplastic polymer.

Some examples of suitable polymers could include polyethylene andpolypropylene. Other suitable polymers could include polycaprolactone,co-polymers of polyethylene-acrylic acid, polyacrylonitrile, polyamides,polybutadiene, polycarbonate, polychloroprene,polychlorotrifluoroethylene, poly(ethylene terephthalate), polyesters ofvarious compositions, polyisoprene, poly(methyl methacrylate),polyoxymethylene, poly(phenylene oxide), polystyrene, polysulfones,polytetrafluoroethylene, poly(vinyl acetate), poly(vinyl chloride),poly(vinylidene chloride), and/or poly(vinylidene fluoride), as well asco-polymers or polymer blends of all sorts.

In other embodiments, the base compound may not be a polymer. Forinstance, the base compound could be another suitable compound that canliquefy and which can be spun in an electrostatic field, or in somecases even a solvent based system in which the solvent either evaporatesor is separated during the dielectric spinning process.

In some cases, suitable base compounds could include molten glasses,molten metals, molten salts, minerals, ceramics, and pure liquidsubstances. Other base compounds could include mixtures, includingpolymer mixtures, as well as suspensions, emulsions, and solutions.

In general, according to the teachings herein, particles (e.g., fibers),and especially sub-micron particles and fibers may be formed by adding adielectric additive to a base compound (e.g., adding glycerol topolypropylene), in some instances in combination with a dispersant. Thebase compound can then be liquefied, if not already a liquid when thedielectric additives are added. For instance, when the base compound isa polymer the polymer could be melted.

In some embodiments, the liquefied base compound can then be subjectedto a strong force attenuation (e.g., mechanical attenuation) to formpre-particles, which in some cases may be micronic. The resultingpre-particles may then be spun in an electrostatic field (e.g.,dielectrically spun) for example using the apparatus 10 as generallydescribed above or another suitable apparatus.

More particularly, the liquefied base compound can be exposed to anelectrostatic field when in a pre-particle state so that theelectrostatic field can further attenuate the particles and fibrils toform very small particles (particularly nanoparticles or sub-micronicparticles).

In general, a liquefied base compound may be mechanically attenuated toform the larger pre-particles (e.g., particles larger than one micron),which are further attenuated electrically by the electrostatic field(e.g., by dielectric spinning) to obtain the desired final particle size(e.g., particles less than one micron).

In some embodiments, mechanical attenuation may be done using one ormore rotating surfaces (e.g. the rotating disc 12 described above),rotating capillaries (as described, for example, in PCT Application No.PCT/CA2009/000324 to Koslow), attenuation machines by DuPont, and so on.Mechanical attenuation could also be achieved by melt blowing, gravity,driving a spin-bonding using hypersonic air, fibrillating, and usingvarious other techniques.

In general, the purpose of the mechanical or strong force attenuation isto overcome surface tension and other forces that, on a macroscopicscale, can inhibit particle attenuation within an electrostatic field.Thus, the liquid mixture can be reduced to pre-particles having a sizesufficiently small such that dielectric spinning can become the dominantattenuation mechanism.

At some particle size, the strong forces required to perform furtherattenuation can become too high. At this point, dielectrophoretic forcestend to become dominant and can be used for further attenuation.

In particular, once the pre-particles are sufficiently small due tomechanical or other strong force attenuation (e.g., less than 20microns, or even less than 12 microns or 5 microns), dielectrophoreticforces become dominant and the pre-particles can be successfully furtherattenuated by dielectric spinning (e.g., spinning in an electrostaticfield) to achieve the desired sizes.

Dielectric spinning is usually preceded by “strong force” attenuation(e.g., mechanical attenuation) so that dielectrophoretic forces do notneed to do all the attenuation. More particularly, “strong force”attenuation may be more efficient at producing pre-particles of certainsizes (e.g., micronic pre-particles) prior to dielectric spinning.

In general, in some embodiments pre-particles can be formed using anysuitable melt blown techniques, which could include using a rotatingdisc or one or more various other techniques.

In some embodiments, dielectric spinning could be done without a “strongforce” (e.g., mechanical) attenuation. For example, dielectric spinningaccording to the teachings herein could pull fibers or particlesdirectly from a pool of liquid, although this is generally believed tobe much more difficult.

In some embodiments, dielectric additives may be added to the basecompound before the base compound is liquefied (e.g., by dry mixing). Inother embodiments, the dielectric additives may be added to a molten,fluid or liquefied base compound.

For example, when the base compound is a polymer, dielectric additivescould be dry mixed with polymer pellets before the polymer is melted, ormixed into a polymer melt.

In some embodiments, additional compounds may be added as the particlesare collected (e.g., as the mat T) to provide a desired distribution ofparticles therein. For example, additional materials may be depositedonto the collection plate 20 as the mat T is formed. These materialscould include various types of performance enhancing materials, such asfor example carbon, activated carbon, super absorbent polymers,zeolites, clays such as bentonite or kaolin, diatomaceous earth, choppedfibers, ion exchange resins, Teflon powder, adsorbents, absorbents,silicates, aluminas, minerals, ceramics, glass, polymer powders, beads,granules, and more generally powders of all kinds.

At least some of the teachings herein may provide one or more benefitsover other electric spinning techniques, including in particular meltelectrospinning.

For example, the dielectric additives described herein tend to berelatively inexpensive as compared to other additives (e.g., conductiveadditives) used in melt electrospinning. In particular, dielectricadditives may be 10 to 100 times less expensive (or more) and aregenerally used in smaller amounts as compared to the conductiveadditives used in melt electrospinning.

Moreover, although dielectric additives are generally not goodconductors, this may not be a limiting factor to achieve goodattenuation in dielectric spinning. More particularly, attenuation ofparticles using Coulomb forces may actually be much less desirable thandielectrophoretic attenuation that dominates in dielectric spinning.

The dielectric additives as described also tend to be thermally stable,particularly over the temperature ranges associated with polymer melts,and may less toxic than other additives. In some embodiments, thedielectric additives could include food grade non-toxic dielectricadditives.

The dielectric additives as described herein also tend to be highlyeffective at low concentrations. For example, polyglycerol-3 was shownto be very effective at encouraging the formation of small polypropylenefibers at only 4 wt %. Such small concentrations can further reduce thecosts associated with using dielectric additives, and moreover canensure that the generated particles generally retain their desiredmechanical properties without degradation.

The dielectric additives often impart a very low electrical conductivityto the mixture. Nevertheless, they can work well in electrostatic fieldswith very low amperage, which in some cases may be 1-2 orders ofmagnitude less than conventional electrospinning for a given output ofproduct.

This can result in a safer process that requires less energy, usessmaller equipment and is generally less expensive to operate.

In some embodiments, the teachings herein may also allow for much fasterproduction of particles, in some cases up to hundreds of times morequickly as compared to conventional electrospinning.

In some embodiments, the mixing of the various compounds may be achievedaccording to various techniques. For instance, in some cases adispersant (e.g., sodium stearate) is added to a liquid dielectricadditive (e.g., polyglycerol-3) and mixed distributively anddispersively (e.g., by aggressive high-shear mixing with a mixingelement at several thousand rpm for several minutes).

In some embodiments, a dispersant (e.g., sodium stearate) is added to aliquid dielectric (e.g., polyglycerol-3) and mixed distributively anddispersively at an elevated temperature (e.g., 70 degrees Celsius).

In some embodiments, a dispersant (e.g., sodium stearate) is added to aliquid dielectric (e.g., polyglycerol-3) and mixed distributively anddispersively. The mixed dispersant and liquid dielectric are then addedto a polymer (e.g., polypropylene) along with a viscosity reductionadditive (e.g., Irgatec CR-76) and then mixed prior to melting. Oncemelted, the resulting compound can then be mixed distributively anddispersively.

In general, it may be desirable to ensure that a dispersant and liquiddielectric are rigorously mixed prior to being combined with the otheringredients (such as the based compound or polymer and aviscosity-reduction additive such as Irgatec CR-76). This can helpensure that the dielectric additive will disperse well within themixture and ensure that the resulting fiber quality is good.

More particularly in some embodiments the dispersant and liquiddielectric can be mixed at elevated temperatures in order to: (i) lowerthe viscosity and (ii) improve the effectiveness of thesurfactant/dispersant.

While the above description provides examples of one or more apparatus,systems and methods, it will be appreciated that other apparatus,systems and methods may be within the scope of the present descriptionas interpreted by one of skill in the art.

1.-40. (canceled)
 41. A method of forming particles, comprising: a.adding a dielectric additive to a base compound to form a mixture; andb. dielectrically spinning the mixture to form the particles.
 42. Themethod of claim 41, further comprising mechanically attenuating the basecompound before dielectrically spinning the mixture.
 43. The method ofclaim 42, wherein mechanically attenuating the base compound formsparticles larger than one micron, and the dielectric spinning formsparticles smaller than one micron.
 44. The method of claim 42, whereinthe mechanical attenuation forms particles less than 12 microns indiameter.
 45. The method of claim 42, wherein the mechanical attenuationforms particles less than 20 microns in diameter.
 46. The method ofclaim 42, wherein the mechanical attenuation is performed using at leastone rotating surface.
 47. The method of claim 41, wherein the basecompound is a polymer.
 48. The method of claim 47, further comprisingmelting the polymer to form a liquid polymer melt, then electrospinningthe liquid polymer melt to form polymer particles.
 49. The method ofclaim 48, wherein the dielectric additives are added to the polymerbefore melting the polymer.
 50. The method of claim 48 wherein thedielectric additives are added to the polymer after melting.
 51. Themethod of claim 41, further comprising adding a dispersant selected toencourage the dielectric additive to disperse within the base compound.52. The method of claim 51, further comprising mixing the dispersant anddielectric additive before the dielectric additive is combined withother ingredients.
 53. The method of claim 52, wherein the dispersantand dielectric additive are mixed, then combined with the base compound,and then mixed prior to melting the base compound.
 54. The method ofclaim 52, wherein the dispersant and dielectric additive are mixed, thencombined with the base compound, and then mixed after melting the basecompound.
 55. The method of claim 41, further comprising adding aviscosity reducing additive to base compound.
 56. The method of claim41, wherein the particles include fibers.
 57. The method of claim 41,wherein the particles include droplets.
 58. The method of claim 41,wherein the base compound is selected from the group consisting of: a.liquid polymers; b. molten glasses; c. molten metals; d. molten salts;e. minerals; f. ceramics; g. pure liquid substances; h. suspensions; i.emulsions; j. colloids; k. latex; l. solutions; and m. mixtures.
 59. Themethod of claim 41, further comprising adding at least one additionalcompound.
 60. The method of claim 59, wherein the at least oneadditional compound is selected from the group consisting of: a. carbon;b. activated carbon; c. super absorbent polymers; d. zeolites; e.bentonite; f. kaolin; g. diatomaceous earth h. chopped fibers; i. ionexchange resins; j. Teflon powder; k. adsorbents; l. absorbents; m.silicates; n. aluminas; o. minerals; p. ceramics; q. glass; and r.beads.